[MERGE] TreeTransform rolls back on exception (#67699)

[Aaron Bentley]

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Kuno Meyer wrote:
> It's really great news to see a TreeTransform rollback. I played around
> a bit, and I've got the following points:
> 
> On 21.08.2007 17:42, Aaron Bentley wrote:
> 
> [skip]
>> === modified file 'bzrlib/transform.py'
>> --- bzrlib/transform.py    2007-08-16 05:37:08 +0000
>> +++ bzrlib/transform.py    2007-08-21 15:26:59 +0000
>> @@ -108,6 +108,9 @@
>>              except OSError, e:
>>                  if e.errno == errno.EEXIST:
>>                      raise ExistingLimbo(self._limbodir)
>> +            self._deletiondir = urlutils.local_path_from_url(
>> +                control_files.controlfilename('pending-deletion'))
>> +            os.mkdir(self._deletiondir)
> 
> Why not complain about an already existing pending-deletion dir? As far
> as I can see, the reasons for complaining are not that different than in
> the case of the already existing limbo dir: if pending-deletion exists,
> then a tree transformation has unexpectedly terminated and name
> conflicts during further operation are very likely to occur.

Yes, it's pretty much the same.  I just assume pending-deletion and
limbo will either both exist or both not exist.

>> +            os.rmdir(self._deletiondir)
> 
> Why not use osutils.rmtree()? It would deal with write-protected files
> which can be moved, but not deleted (on Windows).

At this point, the directory should be empty.

> It would be a big gain in user-friendliness if bazaar would tell the
> user which file causes the conflict

I think Python exceptions should include the pathname.

Failing that, we should be raising our own exceptions that include the
pathname.

>, for example by a warning message
> before re-raising exceptions at

I think warnings aren't the right way to handle errors.

But this submission is aimed at ending the data-loss potential, not
making it more friendly.

Aaron
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